Miniaturization of microelectronic devices includes crowding more functionality, such as transistors, onto smaller areas of a semiconductive substrate. Some product goals include lower power consumption, higher performance, and smaller sizes. However, the continuous miniaturization of metal-oxide-semiconductor field effect transistor (MOSFET) devices causes problems in the conventional transistor structures.
Some designs proposed to address the problems of miniaturization use transistors with ultra-thin bodies, or transistors where the surface space charge region scales as other transistor dimensions scale down. Dual-gated or double-gated transistor structures also have been proposed to scale down transistors. As commonly used in the industry, “dual-gate” refers to a transistor with a front gate and a back gate which can be driven with separate and independent voltages, and “double-gated” refers to structures where both gates are driven with the same potential. An example of a double-gated device structure is the FinFET. “TriGate” structures and surrounding gate structures have also been proposed. In the TriGate structure, the gate is on three sides of the channel. In the surrounding gate structure, the gate surrounds or encircles the transistor channel. The surrounding gate structure provides desirable control over the transistor channel, but the structure has been difficult to realize in practice.